Step 6d – Final Steps Before The First Pour

I passed my footing inspection today, which means that I am approved to pour my footings.  The inspector verified that my setbacks were correct and also leaned on the forms a bit to make sure they were sturdy.  He also made a visual inspection of everything to ensure that the dimensions were correct.  Overall it was a pretty easy process.  He signed my building permit and was gone after less than 10 minutes.

Over the last few days I had completed the final steps in preparation for the inspection.  These included forming the small point load footing for the stairway, laying out all the cold water supply lines, and setting up the utility sweeps for the electrical, heat pump water heater, and ductless mini split systems.  I also made a few minor adjustments to the forms to straighten out the rebar and make sure they were precisely squared and leveled, and laid out the anchor bolts.

 The inspector had made a small adjustment to my design during the permitting process.  He decided that the foundation needed to be strengthened at one particular point where the opening for the spiral staircase put a lot of weight on two walls of the first level.  At the spot where these walls intersected, he indicated on my plans that I was to pour a small footing under the slab measuring 16″x 16″x 10″.  I built a form for those dimensions using some 2×4’s and OSB, and lined it up at the correct spot so that the top of the form was 4″ below the top of my other forms.  I will pour this at the same time as my footings and then remove the form.  The 4″ above will allow enough space for the slab to be poured over it.

I’ll be running the hot water lines inside the “conditioned space” of the house, meaning that they will stay nice and warm at the same temperature as the house.  The cold water lines, on the other hand, don’t need that kind of insulation so I am running them underneath the slab alongside the rest of the plumbing I had already installed.  I will be using a hybrid type of water supply installation for the cold water lines, meaning it will be halfway between the “trunk and branch” method and the “home run” method.  The hot water lines will be almost exclusively home runs with one minor exception.

The trunk and branch method of water supply means that you have a main water line that travels through the entire house and wherever you have a fixture like a toilet or sink, the line for that fixture will branch off of the main trunk line.  The home run method means that as soon as the water line enters the house it is piped into what is called a manifold, where it immediately branches off into as many lines as there are fixtures in the house.  These branches pipe directly into each individual fixture.  When dealing with hot water lines, the trunk and branch system has a major flaw in that if you want hot water in one of the fixtures and the water currently in the trunk has already cooled off, you have to wait until all of the water in the trunk has exited the fixture before you get hot water.  This is not only annoying but also extremely wasteful.  The home run method uses more piping, but solves this problem, ultimately paying off in the long run.  For cold water lines this isn’t an issue, so I just ran the piping as efficiently as I could to reduce the amount of pex piping I needed to buy.

The last step was to set up the utility sweeps, or chases.  These are conduits that are bent in 90 degree angles at very large radii, so when I am ready to run utility lines into the house I won’t need to cut a hole in the wall or reduce the amount of insulation I have in an exterior wall.  The electrical sweep will house the main electrical lines for the house.  The one for the water heater will house one cold line and one hot line as the water runs back and forth between the hot water tank inside the house and the heat exchanger outside the house.  Many houses have their hot water tanks in the garage which is extremely inefficient because the garage is unconditioned space and will cause the hot water to cool down faster.  The last sweep will house the refrigerant lines for the ductless mini split system as they travel between the heat pump outside and the fan inside.  I ran each of the sweeps from the location I had planned for each of them on an interior wall of the house down through the footing and out to the other side.  I next cut some small pieces of plywood to ensure that concrete wouldn’t spill over and cover the end of the conduits.

Here is the electrical sweep with the grounding electrode attached to the rebar next to it.
Here you can see the plywood that will prevent the concrete from flowing past the main plumbing outlet

Step 6C – Inner Forms, Plumbing and Bracing

I could save a lot of time and some money by pouring the concrete for the footings and slab at the same time, in which case I would be done with the formwork now.  For several reasons, I decided to pour them separately, so I needed to add an additional set of forms before I pour.  The double pour will allow for more control, hopefully resulting in a smoother, more level slab.  It also allows me to insulate the inside of the footing wall, instead of the outside.  You can always add insulation to the outside of the wall anytime you want, but you can never add it to the inside.

I set up the second set of forms exactly 8″ apart from the first set to create the 8″ stem wall required by the local building code.  The set up method was no different than that of the first set of forms: stakes in the ground, forms nailed to the stakes, scrap wood screwed to the forms to hold them tight to each other with no gap in between.  I attached the two forms together with the precise 8″ gap using some scrap wood.  I placed these scraps at the exact locations where my anchor bolts will go.  This way, I can use the scrap wood to hold the bolt while the concrete cures around it.  The conventional way is just to throw the bolts in wherever you “think” you might need them as the concrete is curing.  This often results in bolts ending up where studs or plumbing is supposed to go and needing to be cut and replaced, so the method I’m using is much more efficient.

 

Once the second set of forms were attached and level with the first set, I began straightening them out using the bracing shown here.  The boards may not look pretty, but they are free and I can’t see spending money on temporary bracing.  When it comes time to pour concrete, we will be banging the forms with hammers trying to work the air pockets out of the concrete so I need to ensure the forms won’t move around at all.

With the forms perfectly marking out the edges of the house, I now had a reference to place the plumbing.  Here you see the plumbing for the toilet which has to exit the concrete slab at the precise location where the toilet will go.  Notice that there is not a trap in the pipe because toilets have traps built into them.  When I connect the plumbing for the tub you will see that there is a u-shaped trap under the concrete that will hold a pocket of water and ensure that the gases from the septic tank don’t enter the house.  When bracing the main pipe here, I will need to maintain a downward slope of 1/4″ for every foot of pipe all the way through the line to the septic tank.  I used the builders level again to make sure that I was starting at the right spot.  Using the spec sheet that came with the septic tank, I know that he inlet is exactly 17″ below the top of the inspection ports that are visible from above.

The edge of the forms where the main sewer pipe will exit the concrete is a little less than 10′ from the inlet port, so the pipes must exit that spot 2.5″ above that height (10′ at 1/4″ per ft= 2.5″).  From there it gets much easier as I just had to slope the pipe at 1/4″ per foot until the end of the line.

The last step before the pour will be my electrical and utility sweeps, so be looking out for that in the next post!